The dinosaurs were destroyed when the protective vapor canopy surrounding the earth collapsed. That was the original cause of Noah's flood.

The vapor canopy protected the earth from all UV radiation from the sun. Beneath the canopy, the planet was a tropical paradise from pole to pole. Humans and animals alike were able to live for hundreds of years.

When the canopy fell, the entire landscape of the planet changed. The axis of the earth shifted, giving us ice on the poles and our current climate. Lifespans were greatly reduced, and many species simply never recovered.